A display device utilizing a liquid crystal compound (in this patent application, a liquid crystal compound is used as a generic term for a compound that exhibits a liquid crystal phase and a compound that exhibits no liquid crystal phases but useful as a component of a liquid crystal composition) has been widely used for the display of a watch, a calculator, a word processor or the like. The display device utilizes the refractive index anisotropy, the dielectric anisotropy and so forth of the liquid crystal compound.
A liquid crystal phase includes a nematic liquid crystal phase, a smectic liquid crystal phase and a cholestric liquid crystal phase, and the nematic liquid crystal phase is most widely applied. A display mode includes a DS (dynamic scattering) mode, a DAP (deformation of aligned phases) mode, a GH (guest-host) mode, a TN (twisted nematic) mode, a STN (super twisted nematic) mode, a TFT (thin film transistor) mode, a VA (vertical alignment) mode, an IPS (in-plane switching) mode and a PSA (polymer sustained alignment) mode.
The display device operated in each mode described above contains a liquid crystal composition. A liquid crystal compound included in the liquid crystal composition is required to have a high clearing point and a large elastic constant K33 (K33: a bend elastic constant) in order to further improve characteristics described above. The liquid crystal compound is required to have a high safety when it is used as a component of a liquid crystal composition in which a high insulation (specific resistance) is required for use in a liquid crystal display device having a thin-film transistor mode or the like.
A variety of liquid crystal compounds in which hydrogen on the benzene ring is replaced by fluorine have conventionally been studied as a component of a liquid crystal composition having a high clearing point and a large elastic constant K33 that is usable for liquid crystal display devices having these operating modes (see, Patent documents No. 1 to 3).
For example, the compounds (A) and (B) having a cyclohexane ring and a benzene ring (See, Patent document No. 1). However, these kinds of compounds do not have such a sufficiently high clearing point and a high elastic constant K33 that satisfies market demand. They also do not have a sufficiently wide temperature range of nematic phase.
The compound (C) in which hydrogen on a benzene ring is replaced by methyl is studied (See, Patent document No. 2). However, this compound does not have such a sufficiently high clearing point and a large elastic constant K33 that satisfies market demand.
The compound (D) in which hydrogen on a benzene ring is replaced by fluorine is studied (See, Patent document No. 3). However, it does not have such a sufficiently high clearing point and a large elastic constant K33 that satisfies market demand.
